Ingestive behavior functions to maintain energy, electrolyte and water balance. Feeding involves complex sequences of learned and innate behaviors that are variable between species. The final acts of feeding behavior, ingestion and rejection, however, are stereotyped responses that are directly triggered by gustatory stimuli. These discrete responses can be influenced by experiential and motivational factors. For example, visceral illness and sodium depletion can directly change the response to a particular gustatory stimulus from ingestion to rejection and vice versa. Using a neural hierarchy approach, we have recently examined the neural basis of ingestion and rejection. With the taste reactivity test, it was possible to demonstrate that the discriminative gustatory stimuli which elicit ingestion and rejection in chronic decerebrate and intact rats are identical. Ingestion and rejection are, therefore, organized in the caudal brainstem. Chronic thalamic rats were markedly different than chronic decerebrate rats in their ingestive consummatory behavior. These preparations have more brain than decerebrates, yet execute rejection responses regardless of the triggering gustatory stimulus. All descending forebrain influences are eliminated in these chronic thalamic preparations. In the terms of Jacksonian neurology, these results represent a basic set of responses organized in a lower neural level, which can be modulated from higher levels. The proposed experiments extend this rationale to analyze the neural machinery involved in modifying ingestive consummatory responses. Utilizing the taste reactivity test, the capacity to modulate ingestion and rejection will be examined in four neural levels of chronic rat preparations: intact, decorticate, thalamic and decerebrate. Taste aversion learning and sodium appetite serve as dependent variables in these experiments. Analysis of skilled and consummatory tongue movements is an adjunct methodology. By establishing behavioral boundaries for neural levels it is possible to organize existing data on the effects of focal lesions and neurotoxins on ingestion. A neural hierarchy for the control of ingestive consummatory responses may provide models for neural mechanisms integrating the complex controls for feeding.